Stacking machines for metal sheets



Nov. 9-, 1965 J. ORMONDY I STACKING MACHINES FOR METAL SHEETS 4 Sheets-Sheet 1 Filed March 20, 1963 baa:

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United States Patent 3,216 721 STACKING MACHINES FOR METAL Sl' EETS John Ormondy, 6 Geake St., Coburg, near Melbourne, Victoria, Australia Filed Mar. 20, 1963, Ser. No. 266,556 11 Claims. (Cl. 271-6 4) This invention relates to machines for stacking flat metal sheets, especially sheets of tin plate and black iron as they are discharged in succession by a conveyor or the like, such as the conveyor of a drying oven or other processing apparatus.

In a known type of stacking machine a horizontal endless conveyor arranged to receive the successive sheets extends forwardly from the receiving position to the adjacent side of the upper end of a stacking compartment and this conveyor is operated at a speed such that each sheet is projected forwardly from the discharge end thereof at a velocity such that its leading end strikes the opposite or remote wall of the compartment and then drops into the latter as disclosed in the specification of Australian Patent No. 237,621.

Usually the stacking machine has two stacking compart ments arranged one beyond the other and an extension conveyor is provided to carry the sheets above the first compartment and to discharge them into the second compartment when a stack of the requisite thickness has been accumulated in the former. A wheeled trolley is generally arranged in the bottom of each compartment to receive the stacked sheets and permit of their convenient removal.

It is important to avoid damage to the sheets because if for example a corner or edge of a sheet is bent, the sheet will not lie flat on the stack and the sheets which follow it in rapid succession will pile on top of it and are apt themselves to be scratched or damaged in the process. Any sheets which are bent must usually be discarded because they are unsuitable for feeding to a can making machine or other treatment or forming apparatus, while likewise even surface scratches may damage a protective coating to an extent such that a sheet is unsuitable for its intended purpose.

Delays due to incorrect stacking are of common occurrence with the machines now in common use and much operating time is lost in this way, while in addition each pile up of incorrectly stacked sheets usually contains a number of damaged sheets which must be discarded.

The aforesaid damage to the sheets and the incorrect stacking thereof may arise from several different causes. Thus as previously explained each sheet is projected over the top of the stacking compartment with a velocity such that its leading edge strikes the opposite or back wall. This wall is generally fixed and provided with a lining of rubber or the like to cushion the shock. As however the sheets strike this wall in much the same position the lining is rapidly cut by the sheets so that it requires frequent replacement while the leading edge or a corner of a sheet may catch on this damaged lining so that the following end of the sheet drops onto the stack leaving the sheet in an inclined position, or the leading edge or a corner thereof may be curved or otherwise bent so that it cannot lie flat on the stack.

Also, if a sheet does not lie fiat on the conveyor to which it is transferred from the drying oven or other treatment apparatus, it may be damaged at this position or may suffer subsequent damage, while if it is not quickly and reliably discharged or cleared from this transfer position or receiving station, the following sheets pile on top of it and the conveyor of the treatment apparatus is liable to be damaged. In the specification of prior Patent No. 3,048,257, however, there is disclosed a conveyor clearing device which operates to obviate serious damage at this position and if necessary by stopping the machine.

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Now the general object of this invention is to provide improvements in stacking machines for metal sheets whereby the latter may be stacked at high speeds and with less risk of damage to the sheets or faulty operation of the apparatus.

Accordingly the invention includes a stacking machine of the type wherein flat sheets of ferromagnetic material are discharged in succession by a conveyor or the like into the upper end of a stacking compartment, wherein the conveyor extends above the compartment and includes magnetic means above or above and adjacent the conveyor for retaining the sheets to the underside of the conveyor and means operable by each sheet at a predetermined position to release the sheet whereby it falls from the conveyor and into the stacking compartment.

In one form the conveyor comprises a plurality of spaced belts and the magnetic means is provided above and adjacent at least one of the belts.

In another form the belts are apertured and the magnetic means is provided above at least one of the belts.

The magnets for retaining the sheets to the underside of the conveyor may be either permanent magnets or electromagnets. When electromagnets are used, means are provided for deenergising them at the required position and for this purpose a switch actuating member is preferably arranged for engagement by the leading edge of each sheet.

Preferably means are provided whereby the longitudinal edges of each sheet are released before the central longitudinal portion thereof, or vice versa whereby the sheet is transversely curved so as to be either concave or convex downwardly as it falls from the conveyor, as it is found that the free fall of the sheets may be more reliably predetermined under these conditions.

The invention also includes means for retaining each sheet in the required flat condition on top of a clearing conveyor thereby to increase the traction of the latter and ensure the rapid and reliable discharge of the sheet.

In order that this invention may be more readily understood, reference will be made to the accompanying drawings which illustrate a machine for stacking tin plate or black iron sheets as they are successively discharged from the conveyor of a drying oven.

In these drawings:

FIGURE 1 is a plan view of the forward end of the machine showing its inter relation with the rearward end of the conveyor of a drying oven;

FIGURE 2 is a plan view of the rearward end of the machine;

FIGURE 3 is a view along line 3-3 of FIG. 1; and

FIGURE 4 is a view along line 4-4 of FIG. 2.

The drying oven conveyor 1 is arranged substantially horizontally and to be provided with spaced outwardly projecting forks 2 between which the metal sheets not illustrated are interleaved in the well known way'and as described and illustrated, for example in the specification of the aforesaid prior Patent No. 3,048,257.

The said stacking machine comprises a take-out conveyor 3 embodying a conveyor clearing device substantially as described in the specification of the said prior Patent No. 3,048,257. This take-out conveyor comprises a plurality of horizontal endless belts 4 arranged side by side at a suitable spacing to provide adequate support for the metal sheets as they are successively laid thereon by the forks 2 of the oven conveyor. The length of belts is such that their forward ends do not obstruct the movement of the forks 2 and as illustrated, the two outer sets of belts are adjacent the sides of the forks throughout a greater portion of their length and the inner set of belts extends into the open central portion of the forks.

The said take-out conveyor is mounted on a frame 5 which is supported on a transverse shaft 6 pivotally supported on the oven conveyor frame 7 whereby the conveyor is moved downwards if successive sheets should pile on top of it. The said pivoted frame 5 is normally maintained in a predetermined position by means of counterweights 8, and a switch 9 or the like is provided and arranged to be operated so as to stop the oven conveyor 1 if the take-out conveyor 3 is depressed below a predetermined position due to the pressure exerted on its upper face by the sheets deposited thereon all as described in the said prior patent specification.

For the purpose of the present invention however, a

plurality of electromagnets 10 are arranged legnthwise of the take-out conveyor 3 and only slightly below the *upper stretches on the conveyor belts 4 in order that each sheet when deposited on the take-out conveyor will be magnetically attracted so as to press more firmly against the conveyor belts 4 and so increase the traction exerted by the latter. In other words, the magnets 10 serve to increase the apparent weight of each sheet and increase the frictional resistance between it and the con- -veyor belts 4 so that the sheet will be rapidly accelerated by the latter without substantial slipping and without angular displacement in its own plane. The said sheets are thus more rapidly and more reliably discharged from the transfer position by the take-out conveyor.

As illustrated the several belts 4 of the take-out conveyor are relatively narrow in width and are arranged in 'may vary in length and the main purpose of the magnets is to ensure that the leading edge portion of each sheet is magnetically attracted as the sheet is placed on the conveyor 3 and that this leading edge portion remains magnetically attracted as it is moved forwardly by the conveyor. Thus when long sheets are being handled some of the magnets disposed closer to the oven conveyor preferably remain deenergised.

In lieu of arranging the electromagnets in the spaces between pairs of conveyor bolts it is practicable to use wider belts having the magnets arranged directly below the upper stretches thereof and when this construction is employed the belts may be formed with perforations to expose the magnets therebelow.

It will be apparent also that permanent magnets may be used if desired instead of electromagnets.

The stacking mechanism 12 is provided some distance beyond the discharge end of the take-out conveyor with two stacking compartments 13, 14 arranged substantially in the usual way with the compartment 14 disposed further from the'take-out conveyor than the compartment In the drawings, the compartment 13 is shown in a condition to receive large sheets whereas compartment 14 is arranged to receive small sheets. It is to be understood that during a run, both compartments would be adjusted to receive sheets of the same size.

Each of the stacking compartments is open at its upper end and the level of such upper ends is disposed slightly back wall 20, while a further transverse wall 21 forms a partition between the two compartments. Each of these walls is disposed vertically and comprises a frame 22 fitted with upper and lower pairs of free running pulleys 23, 24 for a spaced series of endless belts 25 which are maintained under tension by springs 26, 27. The stretches of these vertically disposed endless belts thus form the inner and outer surfaces of the three walls, though it is not necessary that they extend continuously across the width of the compartments as comparatively narrow belts arranged at suitably spaced intervals are sufficient for the purpose.

The distance between the discharge end of the takeout conveyor and the said front wall of the first stacking compartment is approximately equal to the length of each compartment in order that should it be necessary to discard sheets before they reach the first compartment 13 they may be deposited in this reject space as hereinafter described.

A suitable elevated frame structure 28 is disposed horizontally above the open upper ends of the stacking compartments 13, 14 and this frame structure extends forwardly therefrom and above the outer or free end portion of the take-out conveyor 3. The said forward end of the elevated frame structure is provided with a transversely extending spindle 29 carrying a plurailty of spaced pulleys 30 mounted beneath the structure for the forward ends of a corresponding number of longitudinally extending endless conveyor belts 31 and corresponding pulleys 32 for the rear ends of the belts are secured to a plurality of coaxial but, longitudinally spaced second driving spindles 33 mounted beneath the elevated frame structure above and somewhat forwardly of the front wall of the first stacking compartment 13. These endless belts 31 have their lower stretches arranged horizontally in transverse alignment and approximately in the same plane as the upper stretches of the several belts 4 of the take-out conveyor, while suitable tensioning pulleys 34 mounted on arms pivoted at their other end to a member 114 carried by the frame structure 28 and tensioned by springs 35. These pulleys 34 are arranged for engagement with the upper stretches of the said conveyor belts 31 on the forward part of the elevated frame structure. These several belts 31 form what may be termed the intermediate conveyor, the forward end portion of which overlaps the rear or outer end portion of the take-out conveyor 3 when the machine is viewed from the side, though the several belts 31 of the intermediate conveyor are disposed out of transverse alignment with the belts 4 forming the take-out conveyor.

Thus as each sheet is discharged from the take-out conveyor 3 it is disposed in contact with the lower stretches of the several belts 31 constituting the intermediate conveyor and in order to enable the sheets to be retained to the underside of the intermediate conveyor the elevated frame structure 28 is provided with a plurality of transversely spaced and longitudinally extending rows of downwardly facing electromagnets 36.

The said intermediate conveyor may comprise a plurality of transversely spaced pairs of groups of narrow belts with a row of electromagnets 36 arranged longitudinally between each pair or each pair of each group thereof or the magnets may be arranged directly above the lower stretches of the belts and the latter may be formed with spaced openings which expose the magnets as described with reference to the take-out conveyor.

As illustrated in FIG. 1, the inner two triplets of narrow belts 31 are transversely spaced with electromagnets 36 positioned thereabove and therebetween whilst one of the outer belts 31 is wider and is provided with rela tively large apertures 37 therein and in this case the electromagnets 36 are positioned as to be exposed through the apertures whilst the other outer belt has smaller apertures 38 through which the magnets 37 are exposed.

As previously explained, the rear transverse spindles 33 of the intermediate conveyor constitutes the driving spindles and the driving pulleys thereon are preferably coated with rubber or other suitable material to minimize slippage of the belts thereon and this construction is preferably employed for the driving pulleys of the various endless conveyors herein described.

If for any reason some of the plates being discharged from the drying oven are to be rejected, the electromagnets 36 associated with the intermediate conveyor may be deenergised in which case the subsequent sheets are not retained to the under-surface of the intermediate conveyor, but are projected forwardly by the take-out conveyor so that they strike the adjacent or outer face 50 of the front wall 19 of the first stacking compartment and so drop into the aforesaid reject space. As previously explained, each of the transverse walls 19, 2t), 21 of the stacking compartments is fitted with a series of free running endless vertical belts 25 so that when the rejected sheets strike the belts while moving forwardly and downwardly, the said belts are free to move downwardly by frictional engagements therewith so that fresh portions of the belts are continuously arranged in the impact zone and damage to the belts 25 is consequently minimized.

A third and longer endless conveyor 51 which also is carried by the elevated frame structure 28 is arranged longitudinally on the latter with its forward end disposed somewhat forwardly of the rear end of the intermediate conveyor, while the rear end is disposed close to the top of the back wall of the second stacking compartment 14.

This third or final conveyor 51 comprises a transversely spaced series of longitudinally extending belts 52 which pass around pulleys 54 coaxial and longitudinally spaced on transverse driving spindles 53 mounted on the elevated frame 28 in advance of the rear end of the intermediate conveyor and in order that the two conveyors may overlap in this way, the belts composing them are arranged out of transverse alignment. The forward end of the lower stretch of the final conveyor is disposed in the same horizontal plane as the lower stretch of the intermediate conveyor so that the sheets will pass smoothly from the latter to the former.

The rear ends of the several belts 52 forming the final conveyor 51 pass around corresponding free pulleys 55 arranged coaxially in the required position, but these rear pulleys are disposed at a lower level so that the lower stretch of the rear end of the conveyor 51 is disposed below the level of the forward end thereof.

Tensioning rollers 56 are arranged to engage the upper stretches of the belts of the final conveyor, each of which rollers is mounted on the free end of an arm 57 the other end of which is pivotally mounted on the elevated frame 28. In addition means are provided for raising and lowering the intermediate portions of the several belts in unison. For this purpose a transversely extending adjusting member 58 is arranged vertically between the upper and lower stretches of the several belts and is guided for vertical sliding movements on the fixed elevated frame structure 28. This vertical member is provided at its upper end with a series of coaxial pulleys or rollers 59 which engage the lower surfaces of the upper stretches of the several belts 52 and is also provided at its lower end with a similar series of rollers 60 which engage the upper surfaces of the lower stretches.

Thus when the vertically movable member 58 is raised, the adjacent portions of the upper stretches are moved upwardly, while due to the tension of the belts the lower stretches thereof also move upwardly so as to remain in contact with the respective lower rollers 60 and vice versa when the vertically movable member is lowered.

The said vertically movable member 58 is provided with spaced racks 61 which are engaged by corresponding pinions 62 on a commonly transversely extending drive shaft 63 so that by turning the latter manually by means of handle 64 the said member is raised and lowered as required.

The said elevated frame structure 28 is also provided with a plurality of rows of electromagnets 65 which ex tend longitudinally for substantially the full length of the third or final conveyor 51. Each of these rows of magnets may be arranged in the space between a correspond ing pair of belts or otherwise as previously described. The magnets forming each row comprise two groups 66, 67 of which one group 66 is located above the first stacking compartment 13, while the other group 67 is arranged above the rear compartment 14 and the front group 66 may be energised and deenergised in unison and separately from the rear group 67.

A switch actuating member 68, 69 is arranged approximately centrally above each stacking compartment 13, 14 so as to be engageable by the leading edges of the successive sheets to be stacked. These switch actuating members 68, 69 are each mounted on a pivotally mounted threaded shaft 79 which are located longitudinally of the machine so the actuating members may be moved to be substantially centrally of the compartment regardless of the size of sheets to be stacked. Each of these switch actuating members comprises an arm 70 which is pivoted to the elevated frame, as illustrated with regard to actuating member 68, about a transverse axis which is located betwen the upper and lower stretches of the final conveyor belts 52 and which normally inclines down wardly and forwardly towards the intermediate conveyor at a steep angle to the horizontal plane. Each of these arms forms a guide for a slide or carriage 71, which is movable upwardly and downwardly thereon and this slide or carriage is provided with pulleys 72, 73 for a free running endless belt 74 which is engaged by the leading edges of the successive sheets and which is thus free to be moved thereby so that the wear thereon is distributed over the length of the belt. The lower pulley 72 for this belt 74 is arranged forwardly of the upper pulley 73 so that the belt which is short in length inclines forwardly and downwardly.

Each slide or carriage 71 is urged downwardly by an associated spring 75 so that it normally engages a limit stop on the respective pivoted arm 70.

The pivoted arm above the front stacking compartment is swung upwardly and forwardly to an inoperative position when it is desired to stack the sheets in the rear compartment and for this purpose it is moved upwardly and downwardly in unison with the aforesaid vertically movable member 58 by which the central portions of the lower stretches of the final conveyor belts 52 are raised and lowered. For this purpose the slide or carriage 71 on the front pivoted arm 70 is to be connected by a cable 76 which extends upwardly therefrom to and around an idler roller 77 and thence rearwardly from the latter to a drum 78 on the drive shaft 63 of the rack pinions 62.

When it is desired to stack the sheets in the front compartment the vertically slidable belt adjusting member 58 is lowered by rotating handle 65 and, simultaneously the pivoted switch operating arm 70 above the front compartment 13 is disposed in its operative position as illustrated. At this time the lower pulleys 60 on the belt adjusting member 58 are disposed below the level of the driving pulleys 54 at the forward ends of the belts 52 so that the latter incline downwardly and rearwardly from the pulleys 54.

However as each sheet is passing from the rear or dis charge end of the lower surf-ace of the intermediate conveyor it is already in contact with the lower surface of the forward portion of the final conveyor 51 and is retained thereto by the corresponding magnets 65 of the group 66 and the magnetic attraction causes the sheet to push the belts 52 upwardly and substantially into contact with the lower face of the elevated frame structure 28. When the leading edge of the sheet reaches the required position it impinges on the short inclined endless belt 74 on the respective switch operating arm 70 and thus pushes the latter forwardly against the return spring 113. This forward movement operates a switch to be described later which opens the circuits of the electromagnets 66 above the first stacking compartment 13. Thus the sheet is released whereby it drops from the belt 52 while continuing its forward movements so that its leading edge strikes the back wall of the front compartment 13 and then descends onto the stack in the latter. On the magnets being deenergized, the sheet not only drops under gravity but, at the same time, the sheet is forced downwardly as the belts 52 assumes the condition illustrated in FIG. 4. As previously explained this back wall is formed by endless free running vertical belts 25 so that the latter are d splaced by the sheet so as to move fresh surfaces thereof mto the impact Zone.

Likewise as the sheet is dropping from the conveyor belt 52 it displaces the free running belt 74 on the switch actuating member 68.

Each stacking compartment is provided with a false front wall 80 which is adjustable towards and from the respective backw-all to enable variations in the length of the sheets to be stacked as previously mentioned with reference to FIG. 4 in which compartment 13 is adapted to receive large sheets and compartment 14 is adapted to receive small sheets and is also adjustable vertically to suit the height of the stack and these false walls also are preferably fitted with vertically disposed free running endless belts 31 similarly to the fixed front, back and partition walls hereinbefore described. These false front walls are preferably fitted to the trolleys 15 and are normally adjusted before the trolley is positioned in the required compartment.

As previously explained, the forward displacement of the switch operating arm causes the electromagnets 65 to be deenergized to release the sheet, but preferably the magnets of the several rows are not deenergized simultaneously as it is found that the sheets are less prone to fall incorrectly if they are transversely curved so as to be either convex or concave downwardly as they fall from the belt 52.

For this purpose, I use three longitudinally extending rows of the said electromagnets 65 with one row thereof disposed along the longitudinal centerline of the machine and the other two rows arranged at equal distances on the opposite sides thereof so as to be disposed above the side edge portions of the sheets. These outer rows of magnets and the conveyor belts associated therewith may be adjustable towards and from the central row to suit the width of the sheets.

If therefore the magnets of the central row are deenergized before the outer rows thereof, the central longitudinal zone of the flexible sheet drops before the side edges so that the sheet is transversely curved and convex downwardly when the outer rows of magnets are deenergized. Likewise if the outer rows are deenergized before the central row the sheet is transversely curved, but is concave downwardly. If necessary more than three rows of magnets may be used with either the inner or the outer rows being deenergized before the remaining magnets.

Any suitable mechanism may be provided to deenergize the rows of magnets in the required sequence as the switch actuating member 68 is being pushed rearwardly. In one construction illustrated with reference to actuating member 69 and endless belt 111 is moved backwards and forwards in unison with the operating arm 70 is fitted with two strikers 82, 83 to engage the respective switches 84, 85, these strikers 82, 83 being so located that one switch is operated in advance of the other. When the sheet is released, the switch operating arm 70 swings forwardly to its normal position whereby the switches are reclosed to energize the magnets to support the next succeeding sheet.

In order to stack the sheets in the rear compartment 14, the vertically slidable belt adjusting member 58 is raised so that the front switch actuating member 68 is also raised to its inoperative position as previously described whereby the magnet group 66 above the front compartment 13 remain permanently energized.

Thus the sheets are retained to the underside of the conveyor belt as they pass above the front compartment and above the forward portion of the rear compartment until they strike the switch actuating member 69 disposed more or less centrally above the latter. Further similar compartments may be provided if necessary.

The electromagnets 10 of the take-out conveyor may be loosely supported in longitudinally extending slots provided in the pivoted frame 5 of that conveyor and the weight of the magnets is partly compensated by means of suitable mounting springs 86 whereby the magnets are free to float. Likewise the downwardly facing electromagnets 36, 65 associated with the intermediate and final conveyors may be arranged in guide slots and supported by springs 87 whereby they also are free to float and so approach more closely the successive sheets retained thereby to the under surfaces of the respective conveyor belts.

The drive means for the several conveyors may be of any desired form but preferably all three of the conveyors are driven from a single source.

One form of drive is from the oven conveyor drive by means of chain 88 which drives sprocket 89. A chain 47 is connected to sprocket 89 and drives spindle 46 through sprocket 90.

The take-out conveyor is driven from spindle 46 by means of chains or belts 91 and sprockets or pulleys 93, 94 and 95. Pulley 95 is in connection with spindle 96 which carries the sprockets 97 which are in driving connection with the driving pulleys of the belts 4 by means of chains 98, sprockets 99 and idler sprockets 100.

The intermediate conveyor and the find conveyor 51 are both driven from spindle 46 by means of gears 44, 45, pulley or sprocket 101, belt or chain 43, sprocket 102 and spindle 42.

Spindle 42 carries pulleys or sprockets 41 which are connected by belts or chains 39 to pulleys or sprockets 40 on spindles 33 to which are connected the driving pulleys 32 of the intermediate conveyor.

Spindle 42 also carries pulleys or sprockets 102'which are connected by belts or chains 103 to pulleys or sprockets 104 on spindles 53 to which are connected the driving pulleys 54 of the final conveyor.

In an alternative form, a singleelectric motor 48 may be mounted on the elevated frame structure 28, as illustrated in broken lines in FIG. 4, and in this case all three conveyors are driven by belt 49 connected between a pulley on the motor 48 and pulley 105 on spindle 42.

In this case there is no connection to sprocket 90 on spindle 46.

In brief the operation of the apparatus is that each sheet in turn is laid on top of the take-out conveyor 3 by the respective fork 2 of the oven conveyor 1, the forward end portion of each sheet being immediately magnetically attracted downwardly by the electromagnets 10 associated with the take-out conveyor 3 whereby the frictional resistance therebetween is increased and the sheet is immediately and reliably accelerated whereby it is discharged over the outer end thereof. Shortly before each sheet passes from the take-out conveyor it engages the under-surface of the intermediate conveyor 31 and provided the electromagnets 36 associated therewith are energized the sheet is retained to the under-surface of this intermediate conveyor and so passes over the reject space and onto the under-surface of the final conveyor 51 and is retained thereto by the first group of electromagnets 66 located above the first stacking compartment 13.

If the sheets are to be stacked in the first compartment 13 the corresponding switch actuating member 68 is disposed in its operative position and thus when this member is engaged by the leading edge of each sheet it is pushed rearwardly to some extent thereby operating the associated switches in sequence so that the electromagnets are deenergized to release the sheet which thus 9 drops from the belt in a transversely curved condition while still maintaining its full velocity. The descending and forwardly moving sheet thus strikes the free running belts 25 forming the backwall of the first stacking com- 'partment 13 and so drops onto the stack therein.

If the sheets are to be stacked in the second compartment 14 the belt adjusting member 58 is raised causing the switch actuating member 68 to be rendered inoperative and the group of electromagnets 66 energized.

The leading edge of each sheet then engages the switch actuating member 69 and the switches 84, 85 are operated in sequence so that the groups of electromagnets 67 are deenergized in sequence and the sheet descends forwardly, strikes the free running belts 25 forming the back wall of the second stacking compartment 14 and so drops onto the stack therein.

The invention is not limited to the use of electromagnets as permanent magnets may be used in lieu of electromagnets in association with each of the three conveyors. When this is done the sheets are released when required above the respective stacking compartment, either by means arranged to push the belt downwardly so as to increase the gap between the magnets and the sheets or alternatively the magnets may be raised with the same result, the required movement being produced in either case by the engagement of the leading end of the sheet with a suitable striker member.

I claim:

' I. A machine for stacking flat sheets of ferromagnetic material comprising a conveyor with spaced endless belts to discharge sheets in succession, a plurality of spaced rows of electro-magnets each extending longitudinally above said conveyor to retain sheets at the underside thereof, thereby placing said belts under tension, a stacking compartment positioned beneath said conveyor, switch means above said stacking compartment, said switch means having two actuated positions in the first of which the magnets in the outer rows are de-energized and in the second of which all magnets are de-energized, and switch actuating means associated with said switch means extending so as to be actuated by a sheet on said conveyor to cause said switch to sequentially assume its first and second actuated positions to discharge said sheets with control assistance from said belts.

2. A machine for stacking flat sheets of ferromagnetic material comprising a conveyor with spaced endless belts to discharge sheets in succession, a plurality of spaced rows of electro-magnets each extending longitudinally above said conveyor to retain sheets at the underside thereof thereby placing said belts under tension, a stacking compartment positioned beneath said conveyor, switch means above said stacking compartment, said switch means having two actuated positions in the first of which the inner magnets are de-energized and in the second of which all magnets are de-energized, and switch actuating means associated with said switch means extending so as to be actuated by a sheet on said conveyor to cause said switch to sequentially assume its first and second actuated positions to discharge said sheets with control assistance from said belts.

3. A stacking machine having a clearing conveyor in association with a sheet supply comprising a discharge conveyor with spaced endless belts having a forward end which forms a continuation of said clearing conveyor, three spaced rows of electromagnets located longitudinally above said discharge conveyor to retain sheets at the underside thereof thereby placing said belts under tension, a stacking compartment positioned beneath said discharge conveyor, switch means located above said stacking compartment, said switch means having two actuated positions in the first of which the outer rows of magnets are de-energized and in the second of which all magnets are de-energized and switch actuating means associated with said switch means extending so as to be actuated by a sheet on said discharge conveyor to cause said switch to sequentially assume its first and second actuated positions to discharge said sheets with control assistance from said belts.

4. A stacking machine having a clearing conveyor in association with a sheet supply comprising a discharge conveyor with spaced endless belts having a forward end which forms a continuation of said clearing conveyor, three spaced rows of electromagnets located longitudinally above said discharge conveyor to retain sheets at the underside thereof thereby placing said belts under tension, a stacking compartment positioned beneath said discharge conveyor, switch means located above said stacking compartment, said switch means having two actuated positions in the first of which the inner row of magnets are de-energized and in the second of which all magnets are de-energized and switch actuating means associated with said switch means extending so as to be actuated by a sheet on said conveyor to cause said switch to sequentially assume its first and second actuated positions to discharge said sheets with control assistance from said belts.

5. A stacking machine having a clearing conveyor in association with a sheet supply comprising a discharge conveyor with spaced endless belts having a forward end which forms a continuation of said clearing conveyor, a plurality of spaced rows of electromagnets located longitudinally above said discharge conveyor to retain sheets at the underside thereof thereby placing said belts under tension, a first stacking compartment positioned beneath said discharge conveyor, a second stacking compartment positioned beneath said discharge conveyor beyond said first stacking compartment, switch means above each stacking compartment, said switch means having two actuated positions in the first of which the inner magnets are de-energized and in the second of which all magnets are de-energized and switch actuating means associated with said switch means extending so as to be actuated by a sheet on said discharge conveyor to cause said switch means to sequentially assume its first and second actuated positions to discharge said sheets with control assistance from said belts.

6. A stacking machine having a clearing conveyor in association with a sheet supply comprising a discharge conveyor with spaced endless belts having a forward end which forms a continuation of said clearing conveyor, a plurality of spaced rows of electromagnets located longitudinally above said discharge conveyor to retain sheets at the underside thereof thereby placing said belts under tension, a first stacking compartment positioned beneath said discharge conveyor, a second stacking compartment positioned beneath said discharge conveyor beyond said first stacking compartment, switch means above each stacking compartment, said switch means having two actuated positions in the first of which the outer rows of magnets are de-energized and in the second of which all magnets are de-energized and switch actuating means associated with said switch means extending so as to be actuated by a sheet on said discharge conveyor to cause said switch means to sequentiaHy assume its first and second actuated positions to discharge said sheets with control assistance from said belts.

7. A stacking machine comprising a clearing conveyor in association with a sheet supply, said clearing conveyor comprising a plurality of spaced belts, a longitudinal row of magnets positioned beneath the upper stretch of at least one of said belts, means whereby certain of said magnets may be de-activated, a discharge conveyor having a forward end which forms a continuation of said clearing conveyor, a plurality of spaced rows of electromagnets located longitudinally above said discharge conveyor to retain sheets at the underside thereof thereby placing said belts under tension, a stacking compartment positioned beneath said discharge conveyor, switch means above said stacking compartment, said switch means having two actuated positions, in the first of which the magnets in the outer rows are de-energized and in the second of which all the magnets are de-energized and switch actuating means associated with said switch means extending so as to be actuated by a sheet on said discharge conveyor to cause said switch means to sequentially assume its first and second actuated positions to discharge said sheets with control assistance from said belts.

8. A stacking machine comprising a clearing conveyor in association with a sheet supply, said clearing conveyor comprising a plurality of spaced belts, a longitudinal row of magnets positioned beneath the upper stretch of at least one of said belts, means whereby certain of said magnets may be de-activated, a discharge conveyor hav ing a forward end which forms a continuation of said clearing conveyor, a plurality of spaced rows of electromagnets located longitudinally above said discharge conveyor to retain sheets at the underside thereof thereby placing said belts under tension, a first stacking compartment positioned beneath siad discharge conveyor, a second stacking compartment positioned beneath said discharge conveyor beyond said first stacking compartment, switch means above each stacking compartment, said switch means having two actuated positions in the first of which the outer rows of magnets are de-energized and in the second of which all magnets are de-energized and switch actuating means associated withsaid switch means extending so as to be actuated by a sheet on said discharge conveyor to cause said switch means to sequentially assume its first and second actuated positions to discharge said sheets with control assistance from said belts.

9. A stacking machine comprising a clearing conveyor in association with a sheet supply, said clearing conveyor comprising a plurality of spaced belts, a longitudinal row of magnets positioned beneath the upper stretch of at least one of said belts, means to selectively de-activate said magnet, an intermediate conveyor in association with the rear of said clearing conveyor forming a continuation thereof, a discharge conveyor in association with the rear of said intermediate conveyor forming a continuation thereof, a plurality of spaced rows of electromagnets located longitudinally above said discharge conveyor to retain sheets at the underside thereof thereby placing said belts under tension, a stacking compartment positioned beneath said discharge conveyor, switch means above said stacking compartment, said switch means having two actuated positions, in the first of which the magnets in the outer rows are de-energized and in the second of which all the magnets are de-energized and switch actuating means associated with said switch means extending so as to be actuated by a sheet on said discharge conveyor to cause said switch means to sequentially assume its first and second actuated positions to discharge said sheets with control assistance from said belts.

10. A stacking machine comprising a clearing conveyor in association with a sheet supply, said clearing conveyor comprising a plurality of spaced belts, a longitudinal row of magnets positioned beneath the upper stretch ated positions in the first of which the inner magnets are de-energized and in the second of which all magnets are de-energized and switch actuating means associated with said switch means extending so as to be actuated by a sheet on said discharge conveyor to cause .said switch means to sequentially assume its first and second actuated positions to discharge said sheets with control assistance from said belts.

11. .A stacking machine comprising a clearing conveyor in association with a sheet supply, said clearing conveyor comprising a plurality of spaced belts, a longitudinal row of magnets positioned beneath the upper stretch of at least one of said-belts, means to selectively de-activate said magnets, an intermediate conveyor in association with the rear of said clearing conveyor forming a con tinuation thereof; a discharge conveyor in association with the rear of said intermediate conveyor forming a continuation thereof, a plurality of spaced rows of electromagnets located longitudinally above said discharge conveyor to retain sheets at the underside thereof therebyplacing said belts under tension, a first stacking compartment positioned beneath said discharge conveyor, a second stacking compartment positioned beneath said discharge conveyor beyond said first stacking compartment, switch means above each stacking compartment, said switch meanshaving two actuated positions in the first of which the outer rows of magnets are de-energized and in the second of which all magnets are de-energized and switch actuating means associated with said switch means extending so as to be actuated by a sheet on said discharge conveyor to cause .said switch meanstosequentially assume its first and second actuated positions to discharge said sheets with control assistance from said belts.

References Cited by the Examiner UNITED STATES PATENTS 2,486,733 11/49 Buccicone 27174.1 2,492,889 12/49 Royal.

2,847,111 8/58 Buccicone 198-41 2,873,843 2/59 Wilson 1984l 3,055,659 9/62 Buccicone 27169 X 3,088,604 5/63 Nilsson 271-887 X M. HENSON WOOD, JR., Primary Examiner.

ROBERT B. REEVES, Examiner. 

1. A MACHINE FOR STACKING FLAT SHEETS OF FERROMAGNETIC MATERIAL COMPRISING A CONVEYOR WITH SPACED ENDLESS BELTS TO DISCHARGE SHEETS IN SUCCESSION, A PLURALITY OF SPACED ROWS OF ELECTRO-MAGNETS EACH EXTENDING LONGITUDINALLY ABOVE SAID CONVEYOR TO RETAIN SHEETS AT THE UNDERSIDE THEREOF, THEREBY PLACING SAID BELTS UNDER TENSION, A STACKING COMPARTMENT POSITIONED BENEATH SAID CONVEYOR, SWITCH MEANS ABOVE SAID STACKING COMPARTMENT, SAID SWITCH MEANS HAVING TWO ACTUATED POSITIONS IN THE FIRST OF WHICH THE MAGNETS IN THE OUTER ROWS ARE DE-ENERGIZED AND IN THE SECOND OF WHICH ALL MAGNETS ARE DE-ENERGIZED, AND SWITCH ACTUATING MEANS ASSOCIATED WITH SAID SWITCH MEANS EXTENDING SDO AS TO BE ACTUATED BY A SHEET ON SAID CONVEYOR TO CAUSE SAID SWITCH TO SEQUENTIALLY ASSUME ITS FIRST AND SECOND ACTUATED POSITIONS TO DISCHARGE SAID SHEETS WITH CONTROL ASSISTANCE FROM SAID BELTS. 